The primary objectives of these studies are to determine if morphine and methadone will affect the nuclear uptake and retention of the gonadal steroids, estradiol 17beta and testosterone, by the brain and/or cells of the anterior pituitary gland, and to determine if the gonadal steroids will alter the uptake and retention of morphine by the central nervous system. In order to accomplish these objectives, autoradiography will be used to determine the precise anatomical sites at which such interactions between narcotics and steroids may occur.